1. Field of Invention
In general, this invention relates to the storage of geographic feature data and more particularly, to a method and apparatus for storing geographic coordinate data in an efficient manner to be utilized for both graphical and navigational processes.
2. Description of the Related Art
Route planning devices are well known in the field of navigational instruments. The method of route planning implemented by known prior art systems depends on the capabilities of system resources, such as processor speed and the amount and speed of memory. As increased system capability also increases system cost, the method of route planning implemented by a navigation device is a function of overall system cost. Some of the higher cost systems implement a nodal analysis in which the route planning system determines every potential path from a present location to a desired location from data stored in memory. The route planning system then examines each potential path and eliminates paths by built-in criteria such as type of road traversed, shortest distances or user inputted preferred routes. The higher cost route planning systems require a great amount of memory storage space to store every potential route, as well as a need for a powerful processor to analyze the enormous amount of data stored in the memory. These route planning systems provide very accurate route planning data with little or no user intervention. While highly accurate navigational devices eliminate user intervention, their corresponding high cost eliminates a potential market which is unwilling to pay the cost associated with the accuracy and the ease of little intervention.
On the other end of the cost spectrum, some lower cost route planning systems implement a straight line approach in determining the distance between a desired destination and a current location. In this approach, the processor creates a straight line from the present location to the final destination and measures that straight line distance. The low cost system route planning data can be highly inaccurate because the system does not take into account actual thoroughfare layouts. For example, if a desired destination is on a mountain, the straight line distance from a current location might be only six miles. However, if the only available road to that destination is a windy road around the mountain entailing 30 miles of actual driving, the route planning distance calculated by a low cost system implementing the straight line method will be inaccurate. Because the low cost systems are so inaccurate, the practicality of their implementation is reduced by their large potential for error.
In order to effectuate a route planning method, most systems require the cartographic data to be stored as a record in memory. Additionally, many of the prior art systems also require the same cartographic data to be stored as a record in memory a second time for use in graphically representing the cartographic data on a display screen. Because the data contained within both records is repetitive, the redundancy creates a burden on the memory resources of the route planning system. This burden increases substantially in the higher cost systems because of the larger amounts of data needed by the system. Thus, both the high cost and the low cost navigational devices unduly burden system resources by the use of separate navigation and graphical record banks.
Current prior art systems have created a spectrum of products in which the degree of navigational accuracy is dictated primarily by the cost of the system. The lower cost systems currently offer a low degree of accuracy inadequate for users. In addition, both the higher cost and the lower cost system burden overall navigational system resources by the duplication of cartographic data. Therefore, there exists a need for a navigational route planning device which is more accurate than current low cost systems, without requiring the more expensive system resources. In addition, there is also a need for a navigational route planning device that does not unnecessarily burden system resources with redundant, duplicative cartographic data